The philosophy of biology . onception is un-sound, or because the physico-chemical reactions thatoccur in material of the organism are of a differentorder from those that occur in inorganic systems—theyare of the same order. The second law of energeticsis subject to limitations, and it is because it is appliedto organic happenings without regard to these limi-tations that it does not describe the activities of theorganism as well as it describes those of inorganicnature. What, then, are these limitations ? We note inthe first place that the laws of thermodynamics applyto bodies of a certain ra
The philosophy of biology . onception is un-sound, or because the physico-chemical reactions thatoccur in material of the organism are of a differentorder from those that occur in inorganic systems—theyare of the same order. The second law of energeticsis subject to limitations, and it is because it is appliedto organic happenings without regard to these limi-tations that it does not describe the activities of theorganism as well as it describes those of inorganicnature. What, then, are these limitations ? We note inthe first place that the laws of thermodynamics applyto bodies of a certain range of size; or at least thepossibility of mathematical investigation (on which,of course, all depends) is hmited to differential ele-ments of mass, energy, and time. We cannot applymathematical analysis to bodies, or time-intervals offinite size, since the methods of the differentialand integral calculus would not strictly be molecules are so small (i cubic centimetre of a gas 116 THE PHILOSOPHY OF BIOLOGY. may contain about x 10^^ of them) that even sucha minute part of a body, or liquid, or gas as approxi-mates to the infinitesimally small dimensions requiredby the calculus, contains an enormous number ofmolecules. Obviously we cannot investigate the individualmolecules. Even if experimental methods could beso applied, such concepts as density, pressure, volume,or temperature would have no meaning. Physics,then, is based on collections of molecules, and the pro-perties of a body are not those of a molecule of the samebody. Such concepts as temperature and pressure are statistical ones, andare applied to the meanproperties of a largenumber of molecules. We can best illus-trate this by consider-ing Maxwells famousfiction of the sortingdemons. Let us im-agine a mass of gas contained in a vessel the wallsof which do not conduct heat. Let there be a par-tition in this vessel also of non-conducting material,and let there be an aperture in this partition greate
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